Upsilon Andromedae

The circle shows the location of the class F star Upsilon
Andromedae (in the constellation Andromeda). A system of four planets orbits the star.

THE PLANETS

*Planet 1 orbits in 4.62 days, has a mass at least 0.62 times
that of Jupiter, and is 0.06 astronomical units from the star (8.9
million kilometers, 5.5 million miles, or 15 percent Mercury's
distance from the Sun).

*Planet 2 orbits in 238 days, has a mass at least 1.8 times that
of Jupiter, and is 0.86 astronomical units from the star (129
million kilometers, 80 million miles.

*Planet 3 orbits in 3.6 years, has a mass at least 10.2 times
that of Jupiter, and is 2.55 astronomical units from the star (383
million kilometers, 236 million miles, or 1.67 times Mars's
distance from the Sun). The orbits of planets 2 and 3 are
moderately eccentric.

*Planet 4 orbits in 10.5 years, has a mass at least that of
Jupiter, and like Jupiter is 5.2 astronomical units from its star.

THE STAR

Upsilon Andromedae is a fourth magnitude (magnitude 4.09)
class F (F8) ordinary dwarf 44 light years away. Its temperature
of 6210 Kelvin and luminosity 3.4 times that of the Sun suggest a mass 1.3 times solar and a
radius 60 percent larger than the Sun. Like most stars with
planets, Ups And is rich in metals, its iron content (relative to
hydrogen) 1.34 times that of the Sun. A roughly twelfth magnitude
red dwarf (class M4.5) companion orbits at a distance from Ups And
proper of at least 750 astronomical units and must take at least
16,000 years to make a full circuit. From the skies in the
planetary system, it would glow like Venus does to us, though with
a reddish cast.